Caseless smoke grenade including polyvinyl chloride binder

ABSTRACT

A caseless smoke generating grenade consists essentially of a cast flexible main charge. The flameless pyrotechnic composition used in the main charge is comprised of substantially equal proportions of zinc oxide and a perchlorate oxidizer distributed throughout a plasticized polymeric resin fuel having a high halogen content. The composition is free of solvent and provides controlled burning coupled with excellent flexibility, cohesive strength and impact resistance.

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e 1, w 111% 1 ate t 1191 1111 3,72%,382 Zilcoslry 1 Apr. 3, 1973 [541CASELESS'SMOKE G RENADE 2,997,375 8/1961 Rumbel et 111. ..149/76 xiNCLUDING POLYVHNYL CHLORIDE 3,052,577 9/1962 Butler et a1 1. BINDER3,467,558 9/1969 Wernette et al.

3,430,569 3/1969 Craneet al. ..l49/84 X [75] Inventor: Hector JosephZ1lcosky, Colebrook,

Conn Primary Examiner-Carl D. Quarforth [73] Assignee: TheEnsign-Biqktordcompany,Sim- A sistant Examiner- E. A. Miller sbury,Conn. 1 Attorney-John M. Prutzman et a1.

[22] P116111- Sept. 23, 1971 ABSTRACT I A l. N PP 0 183,252 A caselesssmoke generating grenade consists essentially of a cast flexible. maincharge. The flameless Cl I pyrotechnic composition used in the maincharge is 149/2, 149/19, 149/76, 14 comprised of substantially equalproportions of zinc [51] I131. Cl ..F42b 27/00, C06Cl 3/00 oxide and mperchlorate oxidizer distributed [58] held of Search "1 2; 102/652throughout a plastieized polymeric resin fuel having a l high halogencontent. The composition is free of solvent and provides controlledburning coupled with ex- [56] References cued cellent flexibility,cohesive strength and impact re- UNITED STATES PATENTS f 2,939,7796/1960 Brock ..l ..l49/76 12 Claims, No Drawings CASELESS SMOKE GRENADEINCLUDING POLYVINYL CHLORIDE BINDER BACKGROUND AND SUMMARY OF THEINVENTION The present invention relates generally to a pyrotechnic-smokeproducing composition and more particularly concerns a new and improvedsmoke composition and to caseless grenades made therefrom.

The white smoke formulation used extensively and successively heretoforehas contained substantially equal proportions of zinc oxide andhexachlorethane.

Upon combustion zinc and ammonium chlorides are produced and are rapidlyhydrolized by moisture in the air to yield the desired clouds of whitesmoke. 1

Frequently a minor amount of metal powder, such as aluminum powder, alsois added to control the burning time of the composition. It also hasbeen recognized that the amount and quantity of smoke generated by suchcompositions can be improved by the addition of perchlorate oxidizers.

These known smoke producing formulations are predominently mixtures ofthe dry granular components consolidated within a compact mass or chargein order to operate effectively and provide the desired controlledburning rate. Such consolidation required compression or compaction ofthe mixture under considerable pressure within a suitably strongcanister or other container. To resist the pressure loads, costly andbulky containers were used. These generally contained small exhaustports which frequently and disadvantageously permitted flaming of thecomposition. Additionally, when the compressed mixture was sub jected toshock, it often fractured and exposed large surface areas of the charge,also resulting in open flaming rather than the development of voluminousclouds of white smoke.

The advisability of utilizing plastic binders with such formulations toimprove the cohesiveness of the charge and provide a consolidated bodyhas been proposed but never proved feasible. This was due at least inpart to the adverse influence of the binder and its solvent on theburning rate of the composition. As a result the binders generallyconstituted only about 2 7 percent of the composition since binderamounts exceeding about 10 percent generally resulted in mixtures whichburned too slowly, the excess binder merely acting as a diluent in thecomposition. Additionally, extra care had to be exercised to remove asmuch of the solvent as possible.

These compositions also had a tendency to burn at relatively highcombustion temperatures, that is at temperatures of about l,O00 C orhigher. This high combustion temperature necessarily resulted indestruction of any additional agent being dispersed and consequentlysmoke formulations incorporating agents such as tear gas or the likeexhibited low operating efficiencies. The high combustion temperaturesalso created a substantial thermal updraft in the area of the smokecanister causing the smoke to rise rapidly and be easily diluted withinthe atmosphere, thereby resulting in lower efficiency of operation.

These low efficiency, low output rate canisters had the additionalinherent disadvantage of becoming quite hot as they discharge theirpyrotechnic contents and thus could constitute a safety hazard to theunsuspecting. Further, after all the agent had been dispersed, the

spent housing or casing could be used in a manner contrary to itsoriginally intended purpose.

Accordingly, it is a primary object of the present invention to providea new and improved pyrotechnic smoke composition of the zinc oxide typehaving a relatively low combustion temperature coupled with high volumesmoke output and characterized by flameless combustion at atmosphericpressure.

Another object of the present invention is to provide a new and improvedzinc oxide type smoke formulation free of hexachlorethane and exhibitinghigh efficiency operation and rapid yet controlled dissemination ofvoluminous clouds of dense smoke. Included in this object is theprovision for a charge of the type described which is easily ignitableeven in the absence of a special ignition mix.

Still another object of the present invention is to provide a new andimproved zinc oxide smoke formulation adapted to being molded, extrudedor otherwise formed into caseless smoke producing charges free of thebulky containers heretofore used to confine the pyrotechnic formulation.Included in this object is the provision for a polymeric smoke producingcharge ex- 5 hibiting excellent flexibility and cohesive strengththereby avoiding rupture upon impact with hard surfaces.

An additional object of the present invention is to provide a caselessgrenade of the type described having a pyrotechnic charge that does notrequire consolidation and can assume a variety of different shapes yetis completely free of solvents that might adversely affect the burningrate of the charge.

A further object of the present invention is to provide a new andimproved caseless smoke grenade, that is, a grenade free of the bulkymetal or noncombustible containers used heretofore, adapted toincorporate additional vapor producing substances such as tear gas,insecticides, cloud nucleants or the like. This object includesprovision for a smoke generating grenade having a relatively low burningtemperature, characterized by flameless combustion at atmosphericpressure and facilitating dispersion of tear. gas or similar agents in ahighly efficient manner without thermal destruction.

Other objects will be in part obvious and in part pointed out more indetail hereinafter.

These and related objects are accomplished in accordance with thepresent invention by providing a solid caseless charge of flamelesssmoke producing pyrotechnic material exhibiting excellent flexibilityand cohesive strength. The pyrotechnic composition consists essentiallyof zinc oxide, ammonium perchlorate oxidizer and a solvent-freeplasticized polymeric resin having a 'high halogen content, such asplasticized polyvinyl chloride.

A better understanding of the objects, advantages,

DESCRIPTION OF A PREFERRED EMBODIMENT As mentioned hereinbefore, thecaseless grenade of the present invention consists essentially of acast, extruded or formed charge of a white smoke formulation thatincludes not only the zinc oxide and ammonium perchlorate componentsused heretofore but also advantageously eliminates the conventionalhexachlorethane and replaces it with a plasticized organic thermoplasticresin having a moderate to high halogen content. Unlike prior zinc oxidecompositions the resin acts not as just a binder for the reactants butas the fuel for the combustion reaction and as a source of halogen forproducing the desired zinc and ammonium chlorides. As mentioned therapid hydrolysis of these chlorides by the moisture in the air isresponsible for the voluminous clouds of white smoke resulting fromcombustion of the composition. At the same time the composition is freeof solvents that adversely affect its burning rate and includes a resinthat serves as a control over the combustion temperature of thecomposition. Although the resultant flameless combustion occurs atrelatively low temperatures, that is at a temperature range of about350500 C, the requisite reaction of the zinc oxide is effectively andefficiently carried out to produce the desired smoke output.

Advantageously the organic plasticizer used in conjunction with thehalogen containing-resin acts as a vehicle for mixing and homogenizingthe components of the formulation while obviating solvents in thesystem. The plasticizer may be of the general purpose type suited foruse with halogen containing polymers such as polyvinyl chloride. Thepreferred plasticizers are generally esters of dibasic acids such asphthalic, adipic, 'maleic, succinic or the like. For exampleplasticizers such as dibutyl and dioctyl phthalate, dihexyl sebacate,dilauryl adipate and the like may be used. These liquid plasticizers,being fully compatible with the resin and of low volatility, become anintegral part of the plastisol composition that serves as a dispersingmedium for the zinc oxide and perchlorate oxidizer as well as a fuel,binder and halogen donor.

The halogenated resins found most suited to functioning both as acombustible organic fuel and as a source of halogen for reaction withthe zinc oxide are the high molecular weight polymers and copolymershaving a moderate to high halogen content, such as vinyl chloride andcopolymers thereof. In this connection the vinyl resins sold by B. F.Goodrich under the trade name Geon, such as Geon 121, have given goodresults. These polymers are high molecular weight homopolymers of vinylchloride having an average molecular weight of about 200,000. The solidparticulate resin has a specific gravity of about 1.4 and an inherentviscosity of about 1.2 as measured by test procedure ASTM-D- 1234-60 A.The preferred material also has a chlorine content of about 56 percent;however, other polymers and copolymers of moderate to high halogencontent such as vinylidene chloride may be employed.

The polymeric resin as received from the supplier is a fine powderhaving a bulk density of about 20-25 lbs/cubic foot and a particle sizesmall enough so that 100 percent of the powder easily passes through a200 mesh screen. The resin is preferably of the stir-in type and ispreferably plasticized with a general purpose plasticizer of the lessvolatile type, such as dioctyl phthalate, using substantially equalproportions of the resin and plasticizer. However, frequently it isdesired to reduce the relative amount of plasticizer to achieve properprocessing conditions.

Excellent results are achieved when substantially equal proportions ofthe plasticized halogenated resin, perchlorate oxidizer and zinc oxideare utilized. However, variations in the amounts of the respectivecomponents are permissible. Accordingly, the plasticized resin orplastisol may broadly vary from about 10 percent by weight up to about60 percent by weight and the amount of zinc oxide and perchlorateoxidizer may be from about 15 percent to about 40 percent of thepyrotechnic smoke producing composition. Surprisingly, formulationsusing less than 15 percent of zinc oxide tend to flame while zinc oxideconcentrations below 2 percent are completely ineffective. Thus thepreferred zinc oxide content is about 18 percent or more. It is alsopreferred in accordance with the present invention to incorporate intothis smoke formulation a minor amount of a supplemental halogen donor,such as ammonium chloride, particularly at medium to low resinconcentration levels, the ammoniu'm chloride serving as an additionalsmoke forming component. Thus, it has been found that the preferredsmoke formulation generally falls within the approximate ranges given inTable I.

TABLE I Parts by Weight Component Range Specific Resin l0-25 l8Plasticizer lO-25 l7 Perchlorate Oxidizer 2035 32 Zinc Oxide l8-4O 34Supplemental Halogen Donor In preparing the white smoke formulation forfabrication into caseless grenades in accordance with the presentinvention the various components generally are mixed in a conventionalmanner so as to obtain full homogeneity thereof. Thus the polyvinylchloride resin is mixed with an equal amount of the liquid plasticizerto form a fluid dispersion or suspension having a pastelike or gelconsistency to which is subsequently added the zinc oxide, ammoniumchloride and ammonium perchlorate. The components are blended in asuitable mixing container to provide the requisite homogeneousdistribution of the components throughout the composition. For safetyconsiderations it is generally preferred that the perchlorate oxidizerbe the last component to be added to the mix. The paste-like mixture isa flammable material having a viscosity of about 200,000 cps. Thismixture is then poured into suitable molds and cast into its desiredshape or added to an extruder for subsequent fabrication into its finalconfiguration. The suitably configured or extruded pieces or charges ofsmoke formulation are then slowly heated at moderate temperature, suchas temperatures of about 300 F for a period of approximately 2 to 3hours.

The resultant charges have a density of about 1.5, exhibit excellentstructural integrity and strength and are relatively insensitive toimpact yet are easily ignited by a cigarette, match or the like even inthe absence of an ignition mix. This resiliency, flexibility and impactresistance makes the formulation particularly well suited to caselessgrenades. It will be appreciated that frequently it may be desirable toprovide a specific grenade structure with a pull wire lighter or otherignition device, or to incorporate a short delay element such as a 5second delay at the ignition portion of the grenade in order tofacilitate its ignition and permit the user to propel the grenade to itsdesired location or to otherwise remove himself from the area of thesmoke generation prior to the ignition of the main pyrotechnic smokeproducing charge.

Where the caseless grenadeis to be used for purposes other than merelythe production of white smoke, such as where it is to produce tear gasvapors or the like for riot control application, the cured cast orextruded charge may be provided with an elongated cavity along thelength thereof and a suitable riot control agent placed therein.Preferably a plurality of such cavities may be provided within thecaseless grenade in order to more fully utilize the combustiblepyrotechnic composition. The tear gas producing riot control agentsfrequently employed are the ortho substituted benzal malononitriles,such as the fluoro, chloro, nitro, cyano or hydroxy substituted benzalmalononitriles. v

It is also within the scope of the present invention to incorporatesuitable color producing agents such as organic dyes in the smokeproducing composition. These may be incorporated into the mix prior tothe casting or extruding operations so long as the dye is not adverselyaffected by the heating operation. Where the dye pellets are sensitiveto temperatures belowabout 350 F, incorporation of the dye is preferablywithheld until after the charge has cooled. As will be appreciated otherdispersible agents, such as insecticides or the'like, may also be addedto the grenade for controlled release upon combustion.

Although varying amounts of the tear gas, dye or other additives may beincorporated into the smoke producing grenade, these additives shouldgenerally constitute less than 50 percent of the total weight of thesmoke grenade or similar device. In fact, in the preferred formulationwherein the dye is mixed with the composition prior to the casting orextruding operation, the dye constitutes only about 35 percent by weightof the total main charge.

It is a further advantageous feature of the present invention that thetotal burning time and, consequently, the mass consumption rate for eachgrenade or other device formed from the smoke formulation of the presentinvention can be easily controlled. The mass consumption rate associatedwith a particular device is reported in terms of the weight per unit oftime and is the product of the linear burning rate. of the composition,the density of the composition and the size of the surface area subjectto combustion. As will be appreciated, for a single composition, thefirst two factors may remain constant yet the mass consumption rate canstill be varied with the surface area under combustion and will increaseor decrease as that area increases or decreases. Thus by simplyproviding a central aperture or elongated cavity along the length of thedevice and permitting the composition to burn radially outwardly, themass consumption rate of a device can be substantially increased overthat for a device of identical composition and construction except forthe central aperture.

The invention will be further described with reference to the followingspecific examples which are provided in order that the present inventionmay be more readily understood. These examples are given by way ofillustration only and are not intended to be a limit on the practice ofthe invention. All amounts are given as parts by weight unless otherwisespecified.

EXAMPLE 1 into a 4-inch long cardboard mold of generally cylindricalconfiguration having a diameter of about 1 inch and the filled moldplaced in an oven at 300 F for 2 hrs. The composition was cooled and theresultant solid charge removed from the cardboard mold. lt exhibitedexcellent flexibility and upon ignition at one end thereof burned incigarette fashion at a rate of about 4 inches/minute.

EXAMPLE II The procedure of Example I was repeated except that the solidcured charge was provided with a central longitudinally extending holeof about one-eighth inch diameter along the entire length thereof. Thisresulted in a four fold increase in the surface area under combustionand a corresponding increase in the mass consumption rate, the entirecharge being consumed in about 15 seconds.

As will be apparent to persons skilled in the art, variousmodifications, adaptations and variations of the foregoing specificdisclosure can be made without departing from the teachings of thepresent invention.

I claim:

1. A flameless pyrotechnic smoke producing composition comprising fromabout 15 to about 40 percent by weight zinc oxide, from about 15 toabout 40 percent by weight oxidizer and greater than about 10 percent byweight of a plasticized resin fuel comprised of an organic plasticizerand a vinyl polymer resin having a moderate to high chlorine content,said composition exhibiting a combustion temperature well below 1,000 C.

2. The composition of claim 1 wherein the polymeric resin includespolyvinyl chloride and the combustion temperature of the composition isabout 500 C and less.

3. The composition of claim 1 including a minor amount of a supplementalhalogen donor capable of serving as an additional smoke formingcomponent.

4. The composition of claim 1 wherein the oxidizer is ammoniumperchlorate.

5. The composition of claim 1 wherein the plasticized resin fuelconstitutes approximately one third the total weight of the pyrotechniccomposition.

6. The composition of claim 1 wherein the organic plasticizer andpolymeric resin are present in substantially equal proportions byweight.

7. The composition of claim 1 comprising 10-25 per cent by weightpolymeric resin, lO-25 percent by weight plasticizer, 20-35 percent byweight perchlorate oxidizer and 1 840 percent by weight zinc oxide.

8. A caseless grenade comprised of a solid, flexible,

impact resistant charge of a flameless pyrotechnic smoke generatingcomposition comprising from about auxiliary agent for dispersion withthe smoke upon combustion of the pyrotechnic composition.

10. The caseless grenade of claim 9 wherein the auxiliary agent is atear gas producing agent.

1 l. The caseless grenade of claim 8 including an ignition mix and delayelement for igniting the charge.

12. The caseless grenade of claim 8 wherein the charge includes a colorproducing agent.

2. The composition of claim 1 wherein the polymeric resin includespolyvinyl chloride and the combustion temperature of the composition isabout 500* C and less.
 3. The composition of claim 1 including a minoramount of a supplemental halogen donor capable of serving as anadditional smoke forming component.
 4. The composition of claim 1wherein the oxidizer is ammonium perchlorate.
 5. The composition ofclaim 1 wherein the plasticized resin fuel constitutes approximately onethird the total weight of the pyrotechnic composition.
 6. Thecomposition of claim 1 wherein the organic plasticizer and polymericresin are present in substantially equal proportions by weight.
 7. Thecomposition of claim 1 comprising 10-25 percent by weight polymericresin, 10-25 percent by weight plasticizer, 20-35 percent by weightperchlorate oxidizer and 18-40 percent by weight zinc oxide.
 8. Acaseless grenade comprised of a solid, flexible, impact resistant chargeof a flameless pyrotechnic smoke generating composition comprising fromabout 15 to about 40 percent by weight zinc oxide, from about 15 toabout 40 percent by weight oxidizer and at least 10 percent by weight ofa plasticized vinyl polymer resin fuel, said resin having a moderate tohigh chlorine content, said composition exhibiting a combustiontemperature well below 1,000* C.
 9. The caseless grenade of claim 8wherein the charge includes up to about 35 percent by weight based onthe weight of the pyrotechnic composition of an auxiliary agent fordispersion with the smoke upon combustion of the pyrotechniccomposition.
 10. The caseless grenade of claim 9 wherein the auxiliaryagent is a tear gas producing agent.
 11. The caseless grenade of claim 8including an ignition mix and delay element for igniting the charge. 12.The caseless grenade of claim 8 wherein the charge includes a colorproducing agent.